*{
    margin: 0;
    padding: 0;
    font-family: "Microsoft Yahei";
}
.controller{
    width:600px;
    margin:auto;
}
.controller>ul{
    list-style-type: none;
    margin-top: 20px;
}
.controller>ul:after{
    content: "";
    display: block;
    height: 0;
    clear: both;
}
.controller>ul>li{
    float:left;
    margin-left:10px;
}
.btn{
    width: 30px;
    height:30px;
    border-radius: 5px;
}
.btn:hover{
    cursor: pointer;
}
.red{
    background-color: red;
}
.black{
    background-color: black;
}
.yellow{
    background-color: yellow;
}
.green{
    background-color: green;
}
.purple{
    background-color: purple;
}
.controller button[class="clear"]{
    float: right;
    position: relative;
    padding: 5px 10px;
    border-radius: 5px;
    top:-32px;
}
.controller button[class="clear"]:hover{
    cursor: pointer;
}
h1{
    font-size:50px;
    color:red;
    position: absolute;
}
#canvas{
    border:10px solid rgb(230,11,9);
}